Particular embodiments generally relate to Darlington transistor configurations.
FIG. 1 shows a traditional layout 100. A base contact mask 102 is placed within a base mask outer edge 104. Emitter mask outer edge 106 is placed within a certain distance from base contact mask 102. The emitter needs to be a certain distance from a base contact. The contact is placed in the outer regions of a base diffusion within the outer base region as defined by base mask outer edge 106. However, during the subsequent processing, the outer base edge moves significantly and is then well outside of the region into which the contact is placed. This region contains no useful features such as an emitter diffusion nor even the contacts themselves. This “empty” volume does however store base charge as well as contribute to collector base capacitance. The problem is that in order to switch from an “ON” state to an “OFF state the drive circuit to a transistor has first to remove this stored charge. Thus the presence of this unnecessary volume adds unnecessary stored charge, which slightly increases the switching time. The added capacitance also has a degrading influence but to a lesser extent.